Add "change_in_name" option to name_new/firstupdate/update

[JeremyRand]

Is your feature request related to a problem? Please describe.

It is desirable in some cases (e.g. when optimizing for minimal fees) to embed the change of a name transaction in the name output instead of creating a separate currency output for the change. Unfortunately, this is not supported by the name RPC methods.

Describe the solution you'd like

Add a change_in_name field to the options parameter in the name RPC methods. This field is a boolean, and defaults to false. If it is set to true, the change is added to the amount in the name output, instead of creating a currency output for the change. This improves parity between name and currency transactions.

Describe alternatives you've considered

N/A.

Additional context

N/A.